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Theory of Evolution
Ch. 15
(15-1) Evolution
• Change of organisms over generations w/
a strong natural modification process
• “Change over time”
Scientific Theories
• Explain data
• Generations of predictions
• Falsifiable
Lamarck’s Theory
• Use & Disuse: parts of body that are used
extensively become larger & stronger
while those that are not used deteriorate
– Acquired traits
Lamarck (cont.)
• Ex:
– Webbed foot = stretching of membrane b/w
toes (water birds)
• 1st to say:
– Organisms change over time
– New organisms are modified descendants of
older types
Darwin & Wallace’s Theory
• Natural Selection: organisms best suited
to their environment reproduce more
successfully than others
• “Survival of the fittest”
Charles Darwin’s
• Voyage on the Beagle
Darwin’s Studying Ground
Darwin’s Observations
• 13 similar but separate species of finches
– Specialized for food
• Similarities lead to belief of a common
ancestor
Darwin’s Conclusions
1. Descent w/ modification
2. Modification by natural selection
Descent w/ Modification
• Newer species are modified descendants
of older species
• All species descended from 1 of a few
original types of life
Modification by Natural
Selection
• How evolution occurs
• Environment limits pop.’s growth
• Not all individuals in a pop. are identical &
environment affects them differently
Natural Selection (cont.)
• Individuals w/ favorable traits reproduce
more often than those w/ unfavorable traits
• Thus favorable traits will be passed down
more often
Adaptation
• Inherited trait that inc. an organism’s
chance of survival in a particular
environment
– Based on genes
Fitness
• Ability to survive to propagate their genes
(have babies)
Lamarck vs. Darwin
(15-2) Evidence of Evolution
1. Biogeography
•
Geographical distribution of species
2. Fossil Record
•
Type & order of fossils
Evidence (cont.)
3. Homologous structures
•
Similar b/c of common ancestry
4. Comparative embryology
•
Study of structures that appear during
embryonic development
5. Molecular biology
•
DNA & proteins
Biogeography
• New organisms arise in same geographic
area where similar forms already lived
• Ex: kangaroos only in Australia
Fossil Record
• Fossils: impressions of organisms from the
past mineralized in rock
• Links b/w modern forms & ancestors
Distribution of Fossils
• Law of superposition: lowest layers of rock
are oldest
• Fossil-bearing strata show when
organisms became extinct
• Mass extinction: brief period in which large
#’s of species disappeared
Homologous Structures
• May have different functions but have
similar anatomy
• Shows a common ancestor
• Ex: bird beaks & forelimbs
Common Ancestor
Analogous Structures
• Similar look & function, but different
embryological development & anatomy
• Ex: bird & insect wings
Vestigial Structure
• Part of an organism w/ little or no function,
but had a function in an ancestral species
• Ex: human tailbone & appendix
Comparative Embryology
• All vertebrate embryos go through a stage
in which they have gill pouches & tails
Molecular Biology
• The more similar the sequence, the more
closely related 2 species are to each other
• DNA, RNA, proteins (amino acids)
Amino Acid Chart
(15-3) Patterns of Evolution
1. Coevolution
2. Convergent Evolution
3. Divergent Evolution
•
Pattern & speed result from changes in
the environment
Coevolution
• Change of 2 or more species in close
association w/ each other
• Ex:
– Predator-prey
– Parasite-host
– Plant-animal pollinator
Convergent Evolution
• Organisms appear to be similar but are not
closely related
• Environment selects similar phenotypes
• Ex: shark & porpoise
Divergent Evolution
• 2 or more related populations become
more dissimilar in response to different
habitats
• Adaptive radiation
– Galapagos finches
• Artificial selection
– Domestic dogs
Divergent
evolution of Grand
Canyon squirrels
Peppered Moth Evolution